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Substrate-Integrated Millimeter-Wave Antennas for Next-Generation Communication and Radar Systems 1st Edition Zhi Ning Chen

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Substrate-IntegratedMillimeter-WaveAntennasforNext-GenerationCommunication andRadarSystems

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LibraryofCongressCataloging-in-PublicationData:

Names:Chen,ZhiNing,editor.|Qing,Xianming,editor.|JohnWiley& Sons,publisher.

Title:Substrate-integratedmillimeter-waveantennasfornext-generation communicationandradarsystems/editedbyZhiNingChen,Xianming Qing.

Othertitles:IEEEPressseriesonelectromagneticwavetheory

Description:Hoboken,NewJersey:Wiley,[2021]|Series:IEEEPress seriesonelectromagneticwavetheory|SeriesinformationfromCIPdata view.|Includesbibliographicalreferencesandindex.

Identifiers:LCCN2021003274(print)|LCCN2021003275(ebook)|ISBN 9781119611110(hardback)|ISBN9781119611127(adobepdf)|ISBN 9781119611158(epub)

Subjects:LCSH:Antennas(Electronics).|Millimeterwavecommunication systems.

Classification:LCCTK7871.6.S832021(print)|LCCTK7871.6(ebook)| DDC621.382/4–dc23

LCrecordavailableathttps://lccn.loc.gov/2021003274

LCebookrecordavailableathttps://lccn.loc.gov/2021003275

CoverDesign:Wiley

Setin9.5/12.5ptSTIXTwoTextbySPiGlobal,Chennai,India 10987654321

Contents

EditorBiographies xi

Contributors xv

Foreword xvii

Preface xix

1IntroductiontoMillimeterWaveAntennas 1 ZhiNingChen

1.1MillimeterWaves 1

1.2PropagationofMillimeterWaves 1

1.3MillimeterWaveTechnology 5

1.3.1ImportantFeatures 5

1.3.2MajorModernApplications 5

1.3.2.1Next-GenerationWirelessCommunications 5

1.3.2.2High-DefinitionVideoandVirtualRealityHeadsets 7

1.3.2.3AutomotiveCommunicationsandRadars 7

1.3.2.4BodyScannersandImaging 7

1.4UniqueChallengesofMillimeterWaveAntennas 8

1.5BriefingofState-of-the-ArtMillimeterWaveAntennas 9

1.6ImplementationConsiderationsofMillimeterWaveAntennas 11

1.6.1FabricationProcessesandMaterialsoftheAntennas 11

1.6.2CommonlyUsedTransmissionLineSystemsforAntennas 12

1.7NoteonLossesinMicrostrip-LinesandSubstrateIntegratedWaveguides 14

1.8UpdateofMillimeterWaveTechnologyin5GNRandBeyond 17

1.9Organizationofthebook 19

1.10Summary 21 References 21

2MeasurementMethodsandSetupsofAntennasat60–325GHzBands 25 XianmingQingandZhiNingChen

2.1Introduction 25

2.1.1Far-FieldAntennaMeasurementSetup 26

2.1.1.1Free-SpaceRangeUsingAnechoicChamber 26

2.1.1.2CompactRange 27

2.1.2Near-FieldAntennaMeasurementSetup 28

2.2State-of-the-ArtmmWMeasurementSystems 29

2.2.1CommerciallyAvailablemmWMeasurementSystems 29

2.2.2CustomizedmmWMeasurementSystems 31

2.3ConsiderationsforMeasurementSetupConfiguration 40

2.3.1Far-FieldversusNear-FieldversusCompactRange 40

2.3.1.1Far-FieldMeasurement 40

2.3.1.2Near-FieldMeasurement 40

2.3.1.3CompactAntennaTestRange 41

2.3.2RFSystem 41

2.3.3InterfaceBetweentheRFInstrumentandAUT 41

2.3.4On-WaferAntennaMeasurement 43

2.3.4.1FeedingandMovementLimitations 43

2.3.4.2ReflectionCausedbyProbes/MetallicEnvironment 43

2.3.4.3UndesiredCouplingEffectsCausedbyMeasurementProbes 44

2.4mmWMeasurementSetupExamples 45

2.4.160-GHzAntennaMeasurementSetup 45

2.4.2140-GHzAntennaMeasurementSetup 45

2.4.3270-GHzAntennaMeasurementSetup 47

2.5Summary 51 References 52

3SubstrateIntegratedmmWAntennasonLTCC 55 ZhiNingChenandXianmingQing

3.1Introduction 55

3.1.1UniqueDesignChallengesandPromisingSolutions 55

3.1.2SIWSlotAntennasandArraysonLTCC 56

3.2High-GainmmWSIWSlotAntennaArraysonLTCC 59

3.2.1SIWThree-DimensionalCorporateFeed 59

3.2.2SubstrateIntegratedCavityAntennaArrayat60GHz 62

3.2.3SimplifiedDesignsandHigh-Order-ModeAntennaArrayat140GHz 69

3.2.3.1140-GHzSlotAntennaArraywithaLarge-Via-FenceDielectricLoading 70

3.2.3.2140-GHzSlotAntennaArraywithaLarge-Via-FenceandLarge-SlotDielectric Loading 73

3.2.3.3140-GHzSlotAntennaArrayOperatingataHigher-OrderMode(TE20 Mode) 75

3.2.4FullySubstrateIntegratedAntennasat270GHz 82

3.2.4.1AnalysisofLTCC-BasedSubstrateIntegratedStructures 83

3.2.4.2FresnelZonePlateAntennainLTCCat270GHz 85

3.3Summary 88 References 88

4BroadbandMetamaterial-MushroomAntennaArrayat60GHzBands 93 WeiLiuandZhiNingChen

4.1Introduction 93

4.2BroadbandLow-ProfileCRLH-MushroomAntenna 96

4.2.1WorkingPrinciple 96

4.2.2ImpedanceMatching 99

4.3BroadbandLTCCMetamaterial-MushroomAntennaArrayat60GHz 100

4.3.1SIWFedCRLH-MushroomAntennaElement 100

4.3.2Self-DecouplingFunctionality 103

4.3.3Self-DecoupledMetamaterial-MushroomSubarray 106

4.3.4Metamaterial-MushroomAntennaArray 107

4.4Summary 110 References 111

5Narrow-Wall-FedSubstrateIntegratedCavityAntennaat60GHz 115 YanZhang

5.1Introduction 115

5.2BroadbandTechniquesforSubstrateIntegratedAntennas 116

5.2.1EnhancementoftheImpedanceMatchingforSIWAntennas 118

5.2.2Multi-ModeSubstrateIntegratedCavityAntennas 121

5.2.3SubstrateIntegratedCavityBackedSlotAntenna 122

5.2.4PatchLoadedSubstrateIntegratedCavityAntenna 130

5.2.5Traveling-WaveElementsLoadedSubstrateIntegratedCavityAntenna 136

5.3SIWNarrowWallFedSICAntennasat Ka-and V -Bands 140

5.3.1SIWNarrowWallFedSICAntenna 141

5.3.2SIWNarrowWallFedSICAntennaArrayat35GHz 145

5.3.360-GHzSIWNarrowWallFedSICAntennaArray 146

5.4Summary 151 References 151

6Cavity-BackedSIWSlotAntennasat60GHz 155 KeGong

6.1Introduction 155

6.2OperatingPrincipleoftheCavity-BackedAntenna 156

6.2.1Configuration 156

6.2.2AnalysisoftheBacking-Cavity 156

6.2.3DesignoftheBacking-Cavity 157

6.3Cavity-BackedSIWSlotAntenna 158

6.3.1FeedingTechniques 158

6.3.2SIWBacking-Cavity 160

6.3.3RadiatingSlot 162

6.4TypesofSIWCBSAs 163

6.4.1WidebandCBSAs 163

6.4.2Dual-BandCBSAs 165

6.4.3Dual-PolarizedandCircularlyPolarizedCBSAs 166

6.4.4MiniaturizedCBSAs 166

6.5CBSADesignExamplesat60GHz 167

6.5.1SIWCBSAwithDifferentSlotWLR 167

6.5.2ArrayExampleswithDifferentWLRsofSlot 169

6.6Summary 172 References 172

7CircularlyPolarizedSIWSlotLTCCAntennasat60GHz 177 YueLi

7.1Introduction 177

7.2KeyTechniquesofmmWCPAntennaArray 177

7.2.1AntennaElementSelection 177

7.2.2ARBandwidthEnhancementMethods 182

7.3WidebandCPLTCCSIWAntennaArrayat60GHz 183

7.3.1WidebandARElement 184

7.3.2IsolationConsideration 186

7.3.3ExperimentResultsandDiscussion 189

7.4Summary 193 References 194

8GainEnhancementofLTCCMicrostripPatchAntennabySuppressingSurface Waves 197 ZhiNingChenandXianmingQing

8.1Introduction 197

8.1.1SurfaceWavesinMicrostripPatchAntennas 197

8.1.2SurfaceWavesEffectsonMicrostripPatchAntenna 199

8.2State-of-the-ArtMethodsforSuppressingSurfaceWavesinMicrostripPatch Antennas 199

8.3MicrostripPatchAntennaswithPartialSubstrateRemoval 202

8.3.1TechniqueofPartialSubstrateRemoval 202

8.3.260-GHzLTCCAntennawithPartialSubstrateRemoval 205

8.4Summary 207 References 208

9SubstrateIntegratedAntennasforMillimeterWaveAutomotiveRadars 211 XianmingQingandZhiNingChen

9.1Introduction 211

9.1.1AutomotiveRadarClassification 211

9.1.2FrequencyBandsforAutomotiveRadars 212

9.1.3Comparisonof24GHzand77GHzBands 213

9.1.4AntennaSystemConsiderationsforAutomotiveRadarSensors 214

9.1.4.1LensAntennaandReflectorAntenna 214

9.1.4.2PlanarAntennas 214

9.1.5FabricationandPackagingConsiderations 216

9.2State-of-the-ArtAntennasfor24-GHzand77-GHzAutomotiveRadars 217

9.2.1SelectedState-of-the-ArtAntennasfor24-GHzAutomotiveRadars 217

9.2.1.1ShortedParasiticRhombicPatchAntennaArraywithLowerCross-Polarization Levels 217

9.2.1.2CompactTwo-LayerRotmanLens-FedMicrostripAntennaArray 218

9.2.1.3SIWParasiticAntennaArrayWithoutFeedingNetwork 220

9.2.1.4SIWPillboxAntennaIntegratingMonopulseAmplitude-ComparisonTechnique 220

9.2.2SelectedState-of-the-ArtAntennasfor77-GHzAutomotiveRadars 221

9.2.2.1SIWSlotArrayforBothMedium-andLong-RangeAutomotiveRadarSensor 221

9.2.2.216 × 16PhasedArrayAntenna/ReceiverPackagedUsingBond-WireTechnique 222

9.2.2.3Antenna/ModuleinPackage 223

9.3Single-LayerSIWSlotAntennaArrayfor24-GHzAutomotiveRadars 225

9.3.1AntennaConfiguration 225

9.3.2SlotArrayDesign 226

9.3.3FeedingNetworkDesign 227

9.3.4ExperimentResults 228

9.4Transmit-ArrayAntennafor77-GHzAutomotiveRadars 231

9.4.1UnitCell 232

9.4.2Four-BeamTransmit-Array 233

9.4.3Results 234

9.5Summary 236 Acknowledgments 236 References 236

10SidelobeReductionofSubstrateIntegratedAntennaArraysatKa-Band 241 TengLi

10.1Introduction 241

10.2FeedingNetworksforSubstrateIntegratedAntennaArray 242

10.2.1SeriesFeedingNetwork 242

10.2.2Parallel/CorporateFeedingNetwork 244

10.2.3FlatLens/Reflector-BasedQuasi-OpticsFeedingNetwork 245

10.2.4PowerDividers 246

10.3SIWAntennaArrayswithSidelobeReductionatKa-Band 247

10.3.1Double-Layer8 × 8SIWSlotArray 247

10.3.1.1ParameterExtractionofRadiatingSlots 247

10.3.1.2FeedingNetwork 249

10.3.1.3SimulationsandExperiments 249

10.3.216 × 16MonopulseSIWSlotArray 251

10.3.2.1SeriesT-JunctionFeedingNetwork 252

10.3.2.2Sum-DifferenceNetwork 253

10.3.2.3SimulationsandExperiments 254

10.4Summary 256 References 257

11SubstrateEdgeAntennas 259 LeiWangandXiaoxingYin

11.1Introduction 259

11.2State-of-the-Art 261

11.2.1End-FireSEAs 261

11.2.2Leaky-WaveSEAs 263

11.3TaperedStripsforWidebandImpedanceMatching 264

11.3.1TaperedTriangularStrips 265

11.3.2TaperedRectangularStrips 266

11.4EmbeddedPlanarLensforGainEnhancement 268

11.4.1EmbeddedMetallicLens 269

11.4.2EmbeddedGapLens 271

11.5PrismLensforBroadbandFixed-BeamLeaky-WaveSEAs 272

11.6Summary 282 References 283

Index 287

EditorBiographies

ZhiNingCHEN (Fellow,IEEEandFellow,SAEng)receivedhisB.Eng.,M.Eng.,andPh.D.degrees inelectricalengineeringfromtheInstituteofCommunicationsEngineering(ICE),China,in1985, 1998,and1993andasecondPh.D.degreefromtheUniversityofTsukuba,Tsukuba,Japan,in2003. From1988to1995,Dr.ChenwasalecturerandlateraprofessorwithICEandapost-doctoral fellowandlateranassociateprofessorwithSoutheastUniversity,Nanjing,China.From1995to 1997,hewasaresearchassistantandlateraresearchfellowwiththeCityUniversityofHong Kong,HongKong.In2001and2004,hevisitedtheUniversityofTsukubatwiceundertheJSPS FellowshipProgram(seniorfellow).In2004,hejoinedtheIBMThomasJ.WatsonResearch Center,Ossining,NY,USA,asanacademicvisitor.In2013,hejoinedthe“Laboratoiredes SignauxetSystèmes,”UMR8506CNRS—Supelec—UniversityParisSud,Gif-sur-Yvette,France, asaSeniorDIGITEOGuestScientist.In2015,hejoinedtheCenterforNortheastAsianStudies, TohokuUniversity,Sendai,Japan,asaseniorvisitingprofessor.From1999to2016,hewasa principalscientist,thehead/manageroftheRFandOpticalDepartment,andatechnicaladvisor withtheInstituteforInfocommResearch(I2 R),Singapore.In2012,hejoinedtheDepartment ofElectricalandComputerEngineering,NationalUniversityofSingapore,Singapore,asa tenuredfullprofessor,theprogramdirector(Industry),andthefounderanddeputydirectorof theAdvancedResearchandTechnologyInnovationCenter.Heisholding/heldtheconcurrent guestprofessorshipsatSoutheastUniversity(ChangjiangChairProfessor),NanjingUniversity, Nanjing,China,TsinghuaUniversity,Beijing,China,ShanghaiJiaotongUniversity,Shanghai, China,TongjiUniversity,Shanghai,UniversityofScienceandTechnologyofChina,Hefei,China, FudanUniversity,Shanghai,DalianMaritimeUniversity,Dalian,China,ChibaUniversity,Chiba, Japan,NationalTaiwanUniversityofScienceandTechnology,Taipei,Taiwan,SouthChina UniversityofTechnology,Guangzhou,China,ShanghaiUniversity,Shanghai,BeijingUniversity ofPostsandTelecommunications,Beijing,YunnanUniversity,Kunming,China,BeijingInstitute ofTechnology,Beijing,andCityUniversityofHongKong.Heiscurrentlythememberofthe StateKeyLaboratoryofMillimeterWaves,SoutheastUniversityandtheStateKeyLaboratoryof TerahertzandMillimeterWaves,CityUniversityofHongKong.Hehasbeeninvitedtodeliver 100+ keynote/plenary/invitedspeechesatinternationalacademicandindustrialevents.Hehas authored660+ academicarticlesandfivebooksentitled BroadbandPlanarAntennas (Wiley,2005), UWBWirelessCommunication (Wiley,2006), AntennasforPortableDevices (Wiley,2007), Antennas forBaseStationsinWirelessCommunications (McGraw-Hill,2009),and HandbookofAntenna Technologies with76chapters(SpringerReferences,2016,asaneditor-in-chief).Hehasalso contributedthechapterstothebooksentitled DevelopmentsinAntennaAnalysisandDesign (IET, 2018), UWBAntennasandPropagation:ForCommunications,RadarandImaging (Wiley,2006), AntennaEngineeringHandbook (McGraw-Hill,2007), MicrostripandPrintedAntennas(Wiley, 2010),and ElectromagneticsofBodyAreaNetworks (Wiley,2016).Heisholding36granted/filed

patentsandcompleted40+ technologylicenseddealswithindustry.Heispioneeringindeveloping smallandwideband/ultrawidebandantennas,wearable/implantedmedicalantennas,package antennas,near-fieldantennas/coils,3-DintegratedLTCCarrays,microwavelensantennas, microwavemetamaterial-metasurface(MTS)-metaline-basedantennasforcommunications, sensing,andimagingsystems.Heiscurrentlymoreinterestedinthetranslationalresearchof MTSsintoantennaengineering.

Dr.ChenwaselevatedaFellowoftheAcademyofEngineering,Singaporein2019for thecontributiontoresearch,development,andcommercializationofwirelesstechnology andaFellowofthe IEEEfor thecontributiontosmallandbroadbandantennasforwirelessapplications in2007.Hewas arecipientoftheInternationalSymposiumonAntennasandPropagationBestPaperAwardin 2010,theCSTUniversityPublicationAwardsin2008and2015,theASEANOutstandingEngineeringAchievementAwardin2013,theInstitutionofEngineersSingaporePrestigiousEngineering AchievementAwardsin2006,2013(twoawards),and2014,theI2 RQuarterlyBestPaperAward in2004,theIEEEiWATBestPosterAwardin2005,severaltechnologyachievementawardsfrom Chinaduring1990–1997aswellasmorethan23academicawardsbyhisstudentsunderhissupervision.In1997,hewasawardedtheJapanSocietyforthePromotionofScience(JSPS)Fellowship toconducthisresearchattheUniversityofTsukuba.Hehasprovidedninelocalandoverseas telecommunicationandITMNCsandSMEswithtechnicalconsultancyserviceasatechnicaladvisor,aguestprofessor,andachiefscientist.HeistheFoundingGeneralChairoftheInternational WorkshoponAntennaTechnology(iWATin2005),theInternationalSymposiumonInfoComm& MechatronicsTechnologyinBiomedical&HealthcareApplication(IS3Tin3Ain2010),theInternationalMicrowaveForum(IMWFin2010),andtheAsia-PacificConferenceonAntennasand Propagation(APCAPin2012).

Dr.Chenhasalsobeeninvolvedinmanyinternationaleventsasgeneralchairs,chairs,andmembersfortechnicalprogramcommitteesandinternationaladvisorycommittees.Heservedasavice presidentfortheIEEECouncilonRFID(2015–2020),deputyeditorinchieffor IEEEJournalof RFID (2018–2020),andadistinguishedlecturersince2015.Heservedasanassociateeditorforthe IEEETRANSACTIONONANTENNASANDPROPAGATION (2010–2016)andasadistinguished lecturerfortheIEEEAntennasandPropagationSociety(2009–2012).Healsoservedasthechairfor theIEEEMTT/APSingaporeChapter(2008)andasthefoundingchairfortheIEEERFIDSingaporeChapter(2015and2019–2020).Dr.CheniscurrentlyservicingthememberforIEEEMTT-29 onaerospaceCommitteeaswellasthegeneralchairof2021IEEEInternationalSymposiumon AntennasandPropagationandUSNC-URSIRadioScienceMeetinginSingapore.

XianmingQING (Fellow,IEEE)receivedhisB.Eng.degreeinelectromagneticfieldengineering fromUniversityofElectronicScienceandTechnologyofChina(UESTC),China,in1985,andPh.D. degreefromChibaUniversity,Japan,in2010.

From1985to1996,Dr.QingwaswithUESTCasateachingassistantfirst,thenalecturer,and lateranassociateprofessorforteachingandresearch.HejoinedNationalUniversityofSingapore (NUS)in1997asaresearchscientistforstudyinghightemperaturesuperconductorantennas. Since1998,hehasbeenwiththeInstituteforInfocommResearch(I2 R,formerlyknownasCenter forWirelessCommunication,CWC,andInstituteforCommunicationResearch,ICR),Agencyfor Science,TechnologyandResearch(A*STAR),Singapore.Heiscurrentlyholdingthepositionof seniorscientistandtheleaderoftheRFGroupinSignalprocessing,RF,andOpticalDepartment. Hismainresearchinterestsareantennadesignandcharacterizationforwirelessapplications.In particular,hiscurrentR&Dfocusesonbeam-steeringantennas,newmaterial/metamaterial-based antennas,near-fieldantennas,medicalantennas,andmillimeter-wave/sub-millimeter-wave antennas.

Dr.Qinghasauthored/co-authored270+ technicalpaperspublishedininternationaljournals orpresentedatinternationalconferences.Heistheeditorof HandbookofAntennaTechnologies (Springer,2016).Hehasalsocontributed10chapterstothebooksentitled Antennasfor SmallMobileTerminals (ArtechHouse,2018), DevelopmentsinAntennaAnalysisandSynthesis (IET,2018), ElectromagneticsofBody-AreaNetworks:Antennas,Propagation,andRFSystems (Wiley-IEEEpress,2016), AntennaTechnologiesHandbook (Springer,2015), Microstripand PrintedAntennas:NewTrends,TechniquesandApplications (Wiley,2010), AntennasforFixed Base-StationsinWirelessCommunications (McGraw-Hill,2009), Ultra-WidebandShort-Pulse Electromagnetics7 (Springer,2007), AntennaforPortabledevices (Wiley,London,England,April 2007).Heisholding21grantedandfiledpatents.HewasarecipientoftheIEEEInternational SymposiumonAntennasandPropagationBestPaperAwardin2010,theCSTUniversityPublicationAwardin2015,andtheIEEEAsiaPacificConferenceonAntennaandPropagationBest StudentPaperAwardin2016.HewasalsoarecipientofElectronicIndustryAdvancementAward (1stClass,SichuanProvince,P.R.China)in1993and1995,ElectronicIndustryAdvancement Award(3rdClass,SichuanProvince,P.R.China)in1995and1997,ScienceandTechnology AdvancementAward(2ndClass,MinistryofElectronicIndustry,P.R.China)in1994,Science andTechnologyAdvancementAward(3rdClass,MinistryofElectronicIndustry,P.R.China)in 1997,IESPrestigiousEngineeringAchievementAward(Singapore)in2006,2013,and2014,and SingaporeManufacturingFederationAwardin2014.

Dr.QingisafellowofIEEE.Heisservingastheassociateeditorof IEEEOpenJournalof VehicularTechnology andthe InternationalJournalofMicrowaveandWirelessTechnologies (CambridgeUniversityPress/EuMA),theeditorialboardmemberof ChineseJournalofElectronics (ChineseInstituteofElectronics).Healsoservedasthegeneralco-chairoftheIEEEAsia-Pacific ConferenceonAntennasandPropagation2015/2018,theInternationalSymposiumonInfoComm&MechatronicsTechnologyinBiomedical&HealthcareApplication2016(IS3Tin3A in2016).HeiscurrentlyservicingasthememberforMTT-26RFID,WirelessSensorandIoT Committeeaswellasthegeneralco-chairof2021IEEEInternationalSymposiumonAntennas andPropagationandUSNC-URSIRadioScienceMeeting.

Contributors

ZhiNingChen

NationalUniversityofSingapore

4EngineeringDrive3,Singapore117583

RepublicofSingapore

E-mail:eleczn@nus.edu.sg;znchen@ieee.org

KeGong

XinyangNormalUniversity 237#,NanhuRoad,Xinyang,464000,People’s RepublicofChina

Email:gongkexynu@163.com

TengLi

SoutheastUniversity

Sipailou2,Nanjing,210096,People’sRepublic ofChina

Email:liteng@seu.edu.cn

YueLi

TsinghuaUniversity

RohmBuilding8-302,TsinghuaUniversity Beijing,100084,People’sRepublicofChina

Email:lyee@tsinghua.edu.cn

WeiLiu

NationalUniversityofSingapore

4EngineeringDrive3,Singapore117583

RepublicofSingapore

E-mail:wei.liu@nus.edu.sg; jocieu.ustc@gmail.com

XianmingQing

InstituteforInfocommResearch(I2 R) 1FusionopolisWay,#21-01Connexis (SouthTower),Singapore138632,Republic ofSingapore

Email:qingxm@i2r.a-star.edu.sg

LeiWang

Heriot-WattUniversity Room2.02,EarlMountbattenBuilding Edinburgh,EH144AS,UnitedKingdom

Email:wanglei@ieee.org

XiaoxingYin

SoutheastUniversity RoomSouth608,LiwenzhengBuilding Sipailou2,Nanjing210096,People’sRepublic ofChina

Email:xxyin@seu.edu.cn

YanZhang

SoutheastUniversity RoomA3415,BldgA3,WirelessValley (WuXianGu),MoZhouDongLu9 Nanjing,211111,People’sRepublicofChina

Email:yanzhang_ise@seu.edu.cn

Foreword

Therearenowmassiveresearcharticlesandpresentationsonthedesignandanalysisofmillimeter waveantennas,providingevidencethatthetopichasreachedanageofmaturity.ProfessorZhi NingChenandhiscolleaguesandformergraduatestudentshavemadesignificantcontributions inthisareaforyears.Thisbookisverytimelyasmanyupcomingwirelesssystemswillbeoperated atmillimeterwavefrequencies,including5Gmobilecommunications,collisionavoidance systemsforcars,autonomouscontrolsystemsforunmannedaerialvehicles,satelliteradarand communicationsystems,andsoforth.

Thereaderswillfindthebookcoveragebothwideanddeep.Afterdescribingthedetailson thefeaturesofmillimeterwavetechnologyanduniquechallengesofantennadesignaswell asmillimeterwavemeasurementtechniquesandexperimentalsetups,varioustechniquesfor improvingtheperformanceofclassicalantennasfortheoperationatmillimeterwaves,realizing byLTCCtechnologies,arereviewedanddisclosed.Thoseantennadesignsincludelow-profile substrate-integratedwaveguideslotantennas,broadbandantennaarraysonmetamaterials, substrate-integratedcavityantennas,cavity-backedsubstrate-integratedwaveguideslotantennas withlargeapertures,circularlypolarizedsubstrateintegratedwaveguideslotantennas,microstrip antennaswithsuppressedsurfacewavelosses,substrateintegratedantennasforautomotive radars,andsubstrateedgeradiatingantennas.Patternsynthesizingtechniquesforachievinglow sidelobearealsoreviewed.

Thebookwillhavewidespreadappealtopracticingengineers,researchscholars,and postgraduatestudents.IwouldliketocongratulateProfessorZhiNingChenandhisco-authors ontheproductionofthisimportanttext,whichwillbeofgreatbenefittotheantennacommunity globally.

ProfessorKwai-ManLuk FREng,FIEEE CityUniversityofHongKong

Preface

Millimeter-wavetechnologieshavealonghistory.Inearly2000,thetopicbecamehotagaindueto theunlicensed60-GHzwirelesscommunicationsforshort-rangelinks(laterIEEE802.11ad).As antennaresearcherswethoughthowwecancontributetotheresearchanddevelopmentofthe newwaveofmillimeter-wavesystems.Afterthecomprehensivestudyoftheuniquechallengesof antennadesignatmillimeter-wavebands,wedecidedtofocusonthreeissues:losscontrol,integration,andtestingsetups.Since2008wehaveconductedthelossanalysisofalldesignsandproposed technologiestocontrolthelossescausedbymaterials,surfacewaves,andfeedingstructures.We haveexploredalmostallwaystointegratetheantennasandarraysintoavarietyofsubstratefrom printedcircuitboard(PCB),low-temperatureco-firedceramic(LTCC),tointegratedcircuitpackage (ICpackage).Wealsoconfiguredandbuiltupthreemeasurementsystemstotesttheimpedance, radiationpattern,andgainoftheantennasfrom60GHzto325GHz.Ourworkshavebeenwidely recognizedwithtensofpaperspublishedinprestigiousjournals,filedpatents,andcompleted industryprojects.

Withthedeploymentofmillimeter-wavetechnologyin5G,theresearchanddevelopmentof antennatechnologiesatmillimeter-wavebandsarefastadvancingtoindustryapplications.The technologieswedevelopedforalleviatingfundamentalchallengesshouldhavemoreopportunities tobefurtherdevelopedandapplied.

Themajorcontentsofthebookstemfromtheworksofmillimeter-waveantennasinthepast decadewhentheeditorsaswellastheauthorsworkedinInstituteofInfocommResearch(I2R), Singapore.TherelevantresearchanddevelopmentwerefullysupportedbyAgencyforScience, TechnologyandResearch(A*STAR).

Theteamhasworkedhardtocompletethisprojectinashortduration.Allauthorswouldliketo appreciatetheircolleaguesaswellastheirfamilymembersfortheirgeneroussupportwhenthey werepreparingthemanuscripts,inparticular,duringtheCOVID-19period.

ZhiNingChen,NationalUniversityofSingapore XianmingQing,InstituteforInfocommResearch,Singapore

IntroductiontoMillimeterWaveAntennas

ZhiNingChen

DepartmentofElectricalandComputerEngineering,NationalUniversityofSingapore,Singapore117583,RepublicofSingapore.

1.1MillimeterWaves

Millimeterwaves areregulatedbytheInternationalTelecommunicationUnion(ITU)astheelectromagneticwavesatthewavelengthrangeofmillimeterorder,namely,1–10mm;thecorresponding frequencyrangeisfrom30to300GHz,orextremelyhighfrequency(EHF),aslistedinTable1.1. However,thesystemsoperatingatthefrequencieslowerthan30GHz,suchas24GHz,arealsocategorizedasmillimeterwave(mmW)systemssimplybecausethebehaviorsoftheelectromagnetic wavesatsuchfrequenciesareverysimilartothoseatthedefinedmmWfrequencies.Furthermore, thewavesatthewavelengthofsub-millimeterorder,namely0.1–1mm,orthefrequencyrange from300to3000GHz,areregulatedas“terahertz(THz)wave,”andthewavesatthewavelengthof 1mm–1m,orthefrequencyrangefrom300MHzto300GHz,areregulatedas“microwave”byITU [1].Therefore,themmWbandislocatedattheupperedgeofthemicrowaveband.Accordingly, thewavelengthsatthemmWbandsareshorterthanthoseatlowermicrowavebandsbutlonger thanthoseatinfraredbands.

Themajorityofexistingwirelesscommunicationandradarsystemshavebeenlongoperating atthelowermicrowavebands.ThisbookwillfocusonthewavesoverthemmWbandsatthe frequencyrangefrom24to300GHzforwirelessapplications.

1.2PropagationofMillimeterWaves

ThehighfrequenciesorshortwavelengthsofthemmWsmaketheirpropagationcharacteristics veryunique.Thepropagationcharacteristicsdirectlydeterminethebehaviorsofwavespropagating todesireddestinationsthroughacertainpathandmedia.Inalong-distancewirelesscommunication,radar,orimaging/sensingapplication,thepropagationpropertiesofthewavefullydetermine thesystemdesignrequirements,inparticulartheselectionoftheadequateoperatingfrequency andbandwidth[2].

AsshowninTable1.2,thedominantpropagationmodesofthewavesvaryagainstoperating frequencies.Furthermore,thetypesofpropagationmodesdeterminethedistanceofwavepropagation.Itcanbefoundthat:

1.thewavemainlypropagatesinionosphericmodeslikea skywave whenthefrequenciesarelower, forinstance,atveryhighfrequency(VHF)andbelow;

Substrate-IntegratedMillimeter-WaveAntennasforNext-GenerationCommunicationandRadarSystems, FirstEdition. EditedbyZhiNingChenandXianmingQing. ©2021TheInstituteofElectricalandElectronicsEngineers,Inc.Published2021byJohnWiley&Sons,Inc.

Table1.1 AllocationoftheradiofrequencybandsbyITU.

ITUband

numberDesignatedbandFrequencyWavelengthinair

1Extremelylowfrequency(ELF)3–30Hz9993.1–99930.8km

2Superlowfrequency(SLF)30–300Hz999.3–9993.1km

3Ultralowfrequency(ULF)300–3000Hz99.9–999.3km

4Verylowfrequency(VLF)3–30kHz10.0–99.9km

5Lowfrequency(LF)30–300kHz1.0–10.0km

6Mediumfrequency(MF)300–3000kHz0.1–1.0km

7Highfrequency(HF)3–30MHz10.0–100.0m

8Veryhighfrequency(VHF)30–300MHz1.0–10.0m

9Ultrahighfrequency(UHF)300–3000MHz0.1–1.0m

10Superhighfrequency(SHF)3–30GHz10.0–100.0mm

11Extremelyhighfrequency(EHF)30–300GHz1.0–10.0mm

12Tremendouslyhighfrequency(THForTHz)300–3000GHz0.1–1.0mm

Note:

1.Hz:hertz

2.k:kilo(103 ),M:mega(106 ),G:giga(109 ),T:tera(1012 ).

2.thewavecanpropagateinsurfacemodeslikea groundwave whenthefrequenciesareatlow frequency(LF)tohighfrequency(HF)bands;and 3.athigherfrequencies,typicallyVHFandabove,thewavejusttravelsindirectmodes,thatis,the line-of-sight(LOS), wherethepropagationislimitedbythevisualhorizonuptoabout64kmon thesurfaceoftheearth.

TheLOSreferstothewavesdirectlypropagatinginalinefromonetransmittingantennatothe receivingantenna.However,itisnotnecessaryforthewavetotravelinaclearsightpath.Usually, thewaveisabletogothroughbuildings,foliage,andotherobstacleswithdiffractionorreflection, inparticularatlowerfrequenciessuchasVHFandbelow.

Ontheotherhand,likealightwave,alsoanelectromagneticwave,themmWswithshorterwavelengthsinmillimeterorders,inparticular,atEHFandabove,alwayspropagateinLOSmodes.Their propagationissignificantlyaffectedbythetypicalphenomenaofreflection,refraction,diffraction, absorption,andscatteringsothataclearpathwithoutanylossyor/andwavelengthcomparable obstaclesinthetravelingpathisrequired.Suchapropagationfeatureofwaveswillbereflectedin thedesignconsiderationsofantennasinmmWsystems.

Besidestheblockingofobstaclesinthetravelingpath,thepropagationofthemmWsarealso affectedbytheinteractionbetweenthewavesandthemedium,forexample,theatmosphereonthe earth.Figure1.1showstheaverageatmosphericabsorptionofthewavesatsealevel(i.e.,astandard atmosphericpressureof1013.24millibar),atemperatureof20 ∘ C,andatypicalwatervapordensity of7.5gm 3 [3].Theabsorptionisfrequencydependentandignorablewhenthefrequencyislower than,forinstance,20GHzwithanattenuationlessthan0.1dBkm 1 or50GHzwithanattenuation lessthan1.0dBkm 1 .Thisisoneofthekeyreasonsthatalmostallexistinglong-distancewireless systemsoperateatlowerfrequencies,forinstance,sub-6GHzbands.

Table1.2 Dominantpropagationmodesandtypicalapplicationsofelectromagneticwavesatvarious frequencies.

FrequencyWavelengthinair

Extremelylowfrequency (ELF): 3–30Hz

Superlowfrequency (SLF): 30–300Hz

Ultralowfrequency (ULF): 300–3000Hz

Verylowfrequency (VLF): 3–30kHz

Lowfrequency(LF): 30–300kHz

Mediumfrequency(MF): 300–3000kHz

Highfrequency(HF): 3–30MHz

Veryhighfrequency (VHF): 30–300MHz

Ultrahighfrequency (UHF): 300–3000MHz

Superhighfrequency (SHF): 3–30GHz

Extremelyhigh frequency(EHF): 30–300GHz

Tremendouslyhigh frequency(THF): 300–3000GHz

Dominatepropagation modesTypicalapplications

9993.1–99930.8kmGuidedbetweenthe Earthandthe ionosphere

999.3–9993.1kmGuidedbetweenthe Earthandthe ionosphere

99.9–999.3kmGuidedbetweenthe Earthandthe ionosphere

10.0–99.9kmGuidedbetweenthe Earthandthe ionosphere

1.0–10.0kmGuidedbetweenthe Earthandthe ionosphere; groundguided

0.1–1.0kmGroundguided; refractedwavein ionosphericlayers

10.0–100.0mGroundguided; refractedwavein ionosphericlayers

1.0–10.0mLine-of-sight refractedin ionospheric

Verylong-distance wirelesscommunication (underwater/ground)

Verylong-distance wirelesscommunication (underwater/ground)

Verylong-distance wirelesscommunication (underwater/ground)

Verylong-distance wirelesscommunication (underwater/ground)

Verylong-distance wirelesscommunication andbroadcasts

Verylong-distance wirelesscommunication andbroadcasts

Verylong-distance wirelesscommunication andbroadcasts

Wirelesscommunication, radio,andtelevision broadcasts

0.1–1.0mLine-of-sightWirelesscommunication, televisionbroadcasts, heating,positioning, remotecontrolling

10.0–100.0mmLine-of-sightWirelesscommunication, directsatellitebroadcasts, radioastronomy,radar

1.0–10.0mmLine-of-sightWirelesscommunication, radioastronomy,radar, remotesensing,energy weapon,scanner

0.1–1.0mmLine-of-sightRadioastronomy,remote sensing,imaging, spectroscopy,wireless communications

Figure1.1 Theaverageatmosphericabsorptionofwavesatasealevelatthetemperatureof20 ∘ C, standardatmosphericpressureof1013.24millibar,andatypicalwatervapordensity7.5gm 3 [3].

Figure1.2 (a)Apertureantennasand(b)microstripantennas.

Thewaveattenuationiscausedbytheabsorptionofwater(H2 O)and/oroxygen(O2 )intheatmosphere.Thereareseveralabsorptionpeaksacrossthefrequencybandupto400GHz.Thelowest twopeaksappeararoundthe25and60GHzbands,respectively.Inparticular,theattenuationat the60GHzbandis10timesthatofthe30GHzband.Inaddition,thetemperature,pressure,and watervapordensityalsosignificantlyaffecttheabsorption.Itsuggeststhatthewaveattenuationat themmWbandsmayincreasegreatlywhenitisraining,snowing,orfoggy.Suchanobservation mustbeconsideredinthecalculationoflinkbudgetofmmWsystems.Asaresult,theselection anddesignofantennasshouldmeettherequirementsofmmWsystemswithparticularattention touniquenessofwavepropagation.

1.3MillimeterWaveTechnology

1.3.1ImportantFeatures

mmWtechnologyhaslongbeendevelopedforvariouswirelesssystemsinthepastdecadesbecause oftheapparentadvantagesoverthesystemsoperatingatthelowerfrequencybands,thatis,their shorteroperatingwavelengthandwideroperatingbandwidthwiththesamefractionalbandwidth. Theshorteroperatingwavelengthis,forinstance,goodforanimagingsystemwithhigherspatial resolution.Physicallytheresolutionlimitationsinanimagingsystemrestricttheabilityofimaging instrumentstodistinguishbetweentwoobjectsseparatedbyalateraldistancelessthanapproximatelyhalfanoperatingwavelengthofwavesusedtoimagetheobjects.

Withtheshorteroperatingwavelengths,mmWsystemsalsoenjoyanadvantageoverthesystems operatingatlowerfrequencies,namely,atinycomponentsize.Inparticular,theoverallvolumeof themmWdevicescanbegreatlyreducedbecausetheperformanceofsomekeyradiofrequency (RF)componentsaredeterminedbytheelectricalsizeofthedesign,forinstance,antennasand filters.ThesmallersizeoftheRFcomponentsdefinitelybenefitsthedevicedesignsignificantly, especiallyforapplicationsrequiringtinydevicessuchashandsets,wearables,andimplants.For example,itisverychallengingtoinstallmoreantennas,typicallymorethantwoantennasoperating atthebandsof690–960MHzinexistinghandsetswithlimitedoverallspace.However,itiseasyto installmultipleantennasandevenarraysoperatingat,forexample,28or39GHzbandsforthe mobilephonesinfuturefifthgeneration(5G)networks.

AnotherattractiveadvantageisthewideoperatingbandwidthofthemmWsystems.The10% operatingbandwidthata60GHzbandoffersabandwidthof6GHz,10timesthe10%bandwidth at6GHz,namely600MHz.Thewiderabsoluteoperatingbandwidthisabletosupportthetransmissionatmuchhigherdata-ratesaccordingtotheShannon–Hartleytheorem.Thefundamental informationtheorytellsusthatthemaximumtransmissionrateorcapacityoveracommunication channelinthepresenceofnoiseisdirectlyproportionaltoaspecifiedbandwidth[4].Therefore, themmWwirelesscommunicationscaneasilyachievethedata-rateofafewgigabitspersecond (Gbps).

1.3.2MajorModernApplications

ThemmWtechnologyhasalonghistoryinwirelessapplicationssince1890,Hertz’sdays[5]. SelectedkeymilestonesofmmWresearchandtechnologydevelopmentarebriefedinTable1.3.

Withtherapiddevelopmentofmaterials,processing,fabrication,andmeasurementatmmW bands,themmWtechnologyhasbeenfastappliedinmodernwirelesscommunications,radar, imagingscanning,andimagingsystems.Thefollowingsectionsproviderecentexamplesofnew applicationsofmmWtechnology.

1.3.2.1Next-GenerationWirelessCommunications

Wirelesscommunicationsarerapidlyprogressingtowardhighdata-rateandultra-lowlatencyfor theInternetofThings(IoT).Duetotherequirementtosupporthigherdata-rate,mmWtechnologyispromisingfor5Gnetworksoverthefrequencyrangefrom24to86GHz.Investmentonthe researchandtechnologydevelopmentofmmWcellularmobilenetworksandWLAN/WiFiinfrastructuresisincreasingexponentially.Forinstance,mmWtechnologyisthemaincandidateforthe

Table1.3 SelectedkeymilestonesofresearchanddevelopmentofmmWtechnologyby1980s.

PeriodImportantactivitiesTypicalapplicationsSelectedreferences

1890–1945

1947–1965

● HertzandLebedew’s experimentsincentimeter/ millimeterwavelength

● Nichols,Tear,and Glagolewa-Arkadiewa developedinstruments extendedto0.22and0.082mm usingspark-gapgenerator

● CleetonandWilliam developedvacuumtube sources

● BootandRandalldeveloped cavitymagnetronforradar

● Atmosphericattenuation measurementbyBeringer,Van Vleck’sandGordy

● Allcircular-electricmode transmissionwithallRF componentsbyBellLabs

● Geodesiclensantennaby GeorgiaTechnology

● 58-GHzbroad-brandhelix traveling-waveamplifiersby BellLabs

● 150-GHzbackward-wave oscillatorsbyThomson-CSF, France

● Imagingline,itsassociated componentsandsurface-wave propagationonGoubaulineor Sommerfeldwaveonuncoated metalwirebyWiltse

● FirstIREMillimeterand Sub-millimeterConference heldinOrlando,FL,USAin 1963

● FirstspecialissueofTheIEEE ProceedingspublishedinApril 1966

● Confirmed Maxwell’sprediction

● Radiometer

● mmWsources

● 10and24-GHzradar [5–10]

● Point-to-point transmission

● Thefirst14-kmlong transmissionsystem

● Spectroscopy

● 70-GHzradar

● mmWsources

● High-powermmW sources [11–17]

1965–1984

● Developmentofcomponentsat 35,94,140,and220-GHzby USArmyBallisticResearch LaboratoryaswellasRoyal RadarEstablishment,UK

● Thefirstspecialissueofthe IEEETransactiononAntennas andPropagationabout millimeterwaveantennasand propagation.

● Solidstatesource

● Radiometers

● Radars

● Missileguidance

● Communications

Moredetailscanbe foundat[18–20]

conceptofsmallcellsforfuturecellularnetworkimplementation.ThemmWtechnologycanbe usednotonlyformobileterminalsbutalsoforpoint-to-pointbackhauls,tosomedegreetoreplace traditionalfiberoptictransmissionlinesbyconnectingmobilebasestations(BSs).

1.3.2.2High-DefinitionVideoandVirtualRealityHeadsets

Thetransmissionof1080phigh-definition(HD)videoneedsthedata-rateuptogigabitspersecond. Noneoftheexistingwirelessmicrowavelinkscansupportsuchhighspeedatanysub-6GHzbands. The60-GHzmmWtechnologyoperating,forinstance,withunlicensedbandwidthsupto5–7GHz (forexample,US:57.05–64GHzandEurope:57.0–66.0GHz)canbeusedtotransmitHDvideo fromdigitalsettopboxes,laptops,digitalvideodisc(DVD)players,HDgamestations,andother HDvideosourcestoHDtelevision(TV)wirelessly.Furthermore,smalltransmissiondevicescan beintegratedintoTVsetsinvisibly.

SimilartotheHDvideoapplicationsscenarios,virtualreality(VR)applicationsneedultra-high data-ratewirelesslinksinashortrangeforfuturemultimediaapplications.Thewirelesslinkswill supportthehigh-speedtransmissionofvideoandaudiodatafrommobiledevicessuchasheadsets tocontrollingcomputersorotherVRdevices.ThemmWwirelesscommunicationsaretheonly solutiontomeetsuchrequirementssofar.

1.3.2.3AutomotiveCommunicationsandRadars

ThemmWradaroperatingat24GHzmaybethefirstmmWsysteminthehistoryofmmWtechnology,asshowninTable1.3.Recently,autonomousdrivingisbeingdevelopedveryfast.Such applicationsrequiretheultra-high-resolutiondetectionofpedestriansandotherobstructionsas wellascommunicationwithothervehiclesthroughthenetworkinrealtimeandlowlatency. Ultra-high-resolutionradarshavebeendevelopedwiththemmWradarsystemsoperatingata rangefrom77to81GHz.Thedetectionrangevariesfrom0.15to200m.Thecommunicationscan bebuiltuptoachievethegigabitspersecondlinksthrough5Gnetworks.

1.3.2.4BodyScannersandImaging

Duetotheshortwavelengthforpossiblehigh-resolutionimagesandhighfrequencyforfastimaging,themmWtechnologyhasbeenextensivelyappliedinhumanbodyscannerscurrentlyinthe market.ThemmWbodyscannershaveachievedhigh-precisionscanningwithmuchlessharm

Figure1.3 Slotantennas.

Figure1.4 (a)Reflectorantennasand(b)lensantennas.

tothehumanbody.Inparticular,suchmmWfull-bodyscannershavebeenverypopularforairportsecurity.Theyusethetransmittedpoweroflessthan1mWandoperateatafrequencyrange between70and80GHz.

Inconclusion,withitsuniquefeatures,themmWtechnologyhasaverypromisingfutureinthe applicationsofhigh-speedwired/wirelesscommunicationsaswellasradardetectionandimaging.

1.4UniqueChallengesofMillimeterWaveAntennas

Anantennaistheonlymeanstotransfertheelectricpowerfromthecircuitsofawirelesssystem toamediumandviceversa.Therehavebeenmanydesignchallengesforconventionalantennas suchaswideoperationbandwidth,highgainandradiationefficiency,desiredradiationperformance,small/compactsizeandconformalshapes,andlow-costmaterialutilizationandfabrication.However,thedesignofantennasformmWsystemsfacesuniquechallengesbecauseofits higherfrequencies,orshorterwavelengths.

Fromthedesignpointofview:

1. WideBandwidth: AtmmWbands,usuallyweenjoywideavailablespectraforwirelesscommunicationsandradarapplications.Thetypicaloperatingbandwidthismorethan10%forboth requiredimpedancematchinganddesiredradiationperformancesuchasradiationpatterns, radiationefficiency,andpolarization.Itisindeedchallengingfortheantennastomeetalldesign requirementssimultaneously.

2. HighGain: Duetohighoperatingfrequencies,thepath-lossinpropagationatmmWbands,in particularinrainy,foggy,orsnowyweather,becomesmuchmorecriticalthanthatatmicrowave bands.Tocompensateforthehighpath-loss,wemustdesignantennaswithmuchhighergain. Forexample,thegainoftheantennasshouldreachupto15dBifor10mLOSwirelesslinksat 60GHzbandsforsomesystemsundertheIEEE802.11adstandard.

3. HighRadiationEfficiency: Duetohighoperatingfrequencies,theohmiclossescausedbymaterialsandconnectionsinthedesignbecomesevere.Usually,thelossofthedielectricandmetalsincreaseagainstfrequencies.Forinstance,FR4haslosstangentsof0.016at1MHzand

> 0.1at16GHz,respectively.Theotherlosscanbecausedbysurfacewavesduetoelectricallythickdielectricusedinantennadesign.Forinstance,thedielectricsubstrateofapatch antennaincreasesitselectricalthicknessfromatypical0.01operatingwavelengthatafrequency of2.4GHzto0.1wavelengthat24GHzifthesamedielectricsubstrateisusedforthepatch antennadesign.Thethickersubstrateinevitablycausesseverersurfacewaves.Theincreased surfacewavesguidepartoftheradiatedpowertootherdirectionsratherthanthedesireddirection,forinstance,boresight.Suchlosslowerstheradiationefficiencyorgainoftheantenna.

4. Beam-ScanningFunctionality: Duetotheneedofhighgain,thebeamwidthoftheradiation patternisnarrowsothatitisdifficulttoachieveawidecoverage,butitiseasyfortheradiation tobeblockedbyunwantedobstacles.Tokeeppropagationlinksunbroken,thefunctionalityof beam-scanningofantennasisonesolution.Therefore,muchmoreexpensiveandcomplicated antennadesignsarenecessary.

Fromthefabricationandmeasurementpointofview:

1. High-EndMaterialandTightToleranceFabrication: Tokeeplowtheohmiclosscausedinmaterials,high-endmaterials,usuallyathigherprices,mustbeused.Forinstance,FR4isreplaced bymoreexpensivebuthigherperformanceRogersorceramicorliquidcrystalpolymer(LCP). Meanwhile,duetotheshorterwavelengthsathigherfrequencies,higher-precisionfabrication processesareneededtoachieveresultswithintheacceptabletolerance.Forexample,conventionalprintedcircuitboard(PCB)processcanguaranteeatoleranceof0.2mm,whichis0.2% wavelengthat3GHzbut4%wavelengthat60GHz!

2. TestingSetup: Therehavebeenmanyantennatestingsetupsupto40GHzinthemarketandlaboratories.Itisnecessarytoupgradethesetupsandsystemfortheantennatestforthefrequencies higherthan40or67GHz.Expensivefrequencyup-converterheadsarenecessaryforthefrequencyextensionofsuchmmWsystems.ForthemeasurementofimpedanceorS-parameters, high-qualitybutexpensiveconnectorsandcablesmustbeusedtokeeptheinsertionlossacceptable.Inaddition,theon-wafermmWantennameasurementmustbecarriedoutusingprecise andexpensiveprobeswherethemeasurementisusuallyconductedonexpensivespecificprobe stations.Forthemeasurementofradiationperformance,duetothelackoflinkbudgetandthe concernoftestingenvironments,itisnecessarytodesignthesetupbycustomizingthemechanicalstructureswithhigh-precisionlocationandorientation.

Inshort,thedesignofmmWantennasfacesmuchmorelossy,complicated,andcostlyissuesthan thoseatlowermicrowavefrequencies.TheresearchanddevelopmentactivitiesofmmWantenna technologyshouldbedonebytakingallsuchuniquechallengesintoaccount.

1.5BriefingofState-of-the-ArtMillimeterWaveAntennas

Fromanantennaoperationpointofview,mmWantennascanbeanytypeofradiators,suchaswire, aperture,slot,microstrip,reflector,andLensasshowninFigures1.2,1.3,and1.4.Alsotheradiators canbearrangedasarraystoenhancetheirradiatingperformanceandachievemorefunctionalities.However,duetotheuniquechallengescausedbytheirphysicallyshortwavelengths,namely 1mmat300GHzto10mmat30GHzinfreespaceasmentionedabove,sometypesofradiators aremoresuitableformmWantennadesigns,asshowninthegeneraldiscussionlistedinTable1.4. Thediscussionisbasedonthebasicversionsofalltypesofantennadesigns.Avarietyofvariationsoftheantennahavelongbeenproposedforperformanceenhancementaspresentedinthe References[21,22].

Table1.4 mmWantennas.

TypeofradiatorFabrication/TestingPerformance/ApplicationsSketches

Aperture:

● Horn

● Open-end waveguide

● Waveguidehorn

Microstrippatch

● Easyfabricationandtest

● Bulkythree-dimensional geometryformetalstructures

● Difficulttobeintegratedwith circuits

● Lowlossforair-filleddesign

● Possiblyfabricatedusing PCBa) andLTCCb) processes

● Easyfabricationandtest

● Flatandlow-profilegeometry

● Lossyathighfrequencies

● Widefeedingstrips

● Conformalconfiguration

● Easytoformarrays

● Easytobeintegratedwith circuits

● Easytobefabricatedusing PCBandLTCCprocesses

Slot:

● Onground

● Oncavity

● Onwaveguide

Reflector:

● Corner

● Flatplane

● Curvedplane

Lens:

● Luneburg

● Convex-plane

● Concave-plane

● Concave-concave

● Convex-concave

● Convex-concave

● Convex-convex

Wiresandtheir variationson substrate

● Easyfabricationandtest

● Flatgeometry

● Easytoformarrays

● Conformalgeometry

● Difficulttobeintegratedwith circuits

● Noteasyfabricationandtest

● Bulkyandthree-dimensional geometrywithfeed

● Noteasytoformarrays

● Difficulttobeintegratedwith circuits

● Noteasyfabricationbuteasy test

● Bulky,heavyand three-dimensionalgeometry withfeed

● Noteasytoformarrays

● Difficulttobeintegratedwith circuits

● Easyfabricationandtest

● Flatandlow-profilegeometry

● Lossyathighfrequencies

● Widefeedingstrips

● Conformalconfiguration

● Easytoformarrays

● Easytobeintegratedwith circuits

● Easytobefabricatedusing PCBandLTCCprocesses

a)PCB:printedcircuitboard.

b)LTCC:low-temperatureco-firedceramic.

● Moderatebandwidth

● Highgain

● Pointtopointlink

● Standardantennas inmeasurement systems Figure1.2

● Narrowbandwidth

● Lowgain

● Broadsideradiation

● Wideapplications

● Narrowbandwidth

● Lowgain

● Broadsideradiation Figure1.3

● Widebandwidth

● Ultra-highgain

● Directionalradiation

● Widebandwidth

● Ultra-highgain

● Directionalradiation

● Moderatebandwidth

● Lowgain

● Broadside/endfire radiation

Alsotheantennascanbecategorizedintotwoclassesbasedonphysicalgeometry:flat/planarand three-dimensionalstructures.Forhigh-gainapplications,whicharealwaysrequiredformmWsystemsasmentionedpreviously,three-dimensionaldesignssuchasreflectorandlensantennasare perfectoptionsifthereisnospaceandinstallationconstraints;thelarge-scalearraysofplanarelementssuchasmicrostripantennaarraysandslotantennaarraysusuallysufferfromthedifficulty toformthelarge-scalefeedingnetworkinalimitedphysicalspaceandhighlosscausedinthe feedingnetworks.

Asanalternative,atechniqueoflaminatedwaveguidesonPCBsubstratewasinvented [23,24],whichistosomedegreeconsideredtheextensionoftheworkbasedonpost-rodtoform air-waveguides[25].Laterthestructurewascomprehensivelystudiedandnamedassubstrate integratedwaveguide(SIW)andwidelyappliedinmmWantennadesigns[26,27],wherean electromagneticwaveguidingstructureisconstructedbythetwowallsformedbytwoarraysof metalizedvias.Thespacingbetweentheadjacentviasmustmeetthecriteriatostoptheleak ofwavepropagatinginthestructure.Suchasubstrate-integrationtechnologyprovidesmuch flexibilityforwaveguidedesignsandrelevantantennadesigns,inparticular,atmmWbands.

1.6ImplementationConsiderationsofMillimeterWaveAntennas

AtmmWbands,theintegrationofantennasandsubstratebyusingamultilayersubstrateprocess aredesiredforplanarorflatdesignofsystemboards.Thesubstrateintegratedantenna(SIA)can befabricatedexactlyasaconventionalcircuitasforprintedcircuitsonlayeredboards,wherethe antennasbecomepartofcircuitboardsorpackageofintegratedcircuits.Suchintegrationgreatly reducesthelosscausedbytheconnectionbetweenthecircuitsandtheantennas,miniaturizesthe sizeofthesystem,lowersthefabricationcost,andincreasestherobustnessofthesystemwithout additionalinstallationofantennas.Theintegrationoftheantennasonthesubstrateiscritically determinedbyfabricationincludingtheselectionofsubstratematerialsandtheapplicablefabricationprocess.

1.6.1FabricationProcessesandMaterialsoftheAntennas

Withtheshorteroperatingwavelengthsintheorderofamillimeter,thefabricationofmmWantennasneedsatoleranceusuallytighterthanmicrowavetoachievethedesiredperformance.For example,forastraightthinhalf-wavedipoleantennaoperatingat60GHz,theoveralllengthof theantennaisabout2.5mm.Theacceptablefabricationtoleranceistypically0.2%wavelength, namely0.05mm,whichnearlyreachesthelimitoftheconventionalcommercialPCBprocess.The tightertoleranceoffabricationisneedediftheantennasandfeedingnetworkareprintedonthe PCBswiththerelativedielectricconstantlargerthanunit.Therefore,theselectionoffabrication formmWantennaswithfeedingnetworksismorecriticalthanthatatlowermicrowavebands,not onlybecauseofthetolerancebutalsocostsincludingprocessing,materials,andassembling.

AtthemmWbands,multilayeredsubstratessuchaspolytetrafluoroethylene(PTFE),asynthetic fluoropolymeroftetrafluoroethylene,andPTFEcompositefilledwithrandomglassorceramic suchasRT/duroid®arecommonlyusedforlaminatingcircuitsandantennas.PTFE-basedsubstratesusuallyfeaturealowandstablelosstangenttypicallyof0.0018at10GHzandevenhigher andhighresistancetochemicalprocessingandarewaterproofandthermallystable.PTFE-based substrates,however,sufferfromahighercostcomparedtoFR4glassepoxy,aresoftermaterials,and haveahigherthermalexpansioncoefficient.FR4glassepoxyismostcommonlyusedinfrequencies lowerthan3GHzbecauseofitsincreasinglosstangentagainstfrequency.

LCPsareaclassofaromaticpolymers.TheuniquefeatureoftheLCPsubstrateisitssoftness althoughithassimilarpropertiestoPTFE-basedsubstratessuchasextremechemicalresistance, highmechanicalstrengthathightemperatures,andinertness.Itspoorthermalconductivityand surfaceroughnessshouldbetakenintoaccountinelectricalapplications,inparticular,atmmW bands.

Tomeettherequirementsoffabricationtolerance,electrical,andothermechanicalproperties, lowtemperatureco-firedceramic(LTCC)haslongbeenusedasacost-effectivesubstratetechnologyinelectricalandelectronicengineering,especiallyathigherfrequencies.LTCCisamultilayered glassceramicsubstrate.Itisco-firedwithlow-resistancemetalconductors,suchasAuorAg,atlow firingtemperatures,usually ∼850–900 ∘ C,comparedwithhightemperaturemultilayeredceramic sinteredat ∼1600–1800 ∘ C.Therehavebeenmanyceramicmaterialsdevelopedbycommercial companies.Moredetailedinformationcanbefoundinthebook[28],whichstudiesavarietyof electricalmaterialsformmWapplications.Inparticular,theinformationabouttheceramicmaterialsusedinLTCCiscomprehensive.

Forexample,FerroA6MhasbeenwidelyusedinapplicationsatmmWbands.Ithasarelative dielectricconstantof5.9–6.5andlosstangentof ∼0.001–0.005at3GHz.Inparticular,theelectrical propertiesarestableagainstfrequency.TherelativedielectricconstantandlosstangentofDuPont 951ceramicare ∼7.85and0.0063at3GHz,respectively.Itshouldbenotedthattheceramicused inLTCCusuallyhastherelativedielectricconstantsof ∼6–10,sometimes ∼18[29].Highrelative dielectricconstantsareusuallynotdesiredforantennadesignatmmWbandsbecausetheywill shrinkthedimensionsofantennassothatthefabricationneedsmuchhigheraccuracy[30].

WithanLTCCprocess,theLTCCceramicsubstratecanhostalmostaninfinitenumberoflayers. Thethinlayersarestackedoneonthetopofanother.Theconductingpathsofgoldorsilverthick filmpastesareprintedoneachsurfacelayerbylayerusingthesilk-screenprintingmethod.When themultilayersetuphasbeenstackedandprinted,itisthenfiredintheprocessovenwherethe lowsinteringtemperatureallowstheuseofgoldandsilverasconductingtraces.Thesimplified descriptionofprocessincludes:

StepI:viapunch,viaconductorfill,andtraceprinting;

StepII:layerstackandlamination;and

StepIII:layerco-fire.

ThePCBandLTCCprocessesareconciselycomparedinFigure1.5.Fromawaveguidefeeding networkandantennadesignpointofview,themostimportantdifferencebetweenthePCBand LTCCprocessesisthattheLTCCprocessisabletoimplementtheblindviaandembeddedcavity whilethePCBprocessisunabletodoit.

Furthermore,theLTCCusedforSIAdesignsalsoincreasestheadvantagessuchaslowloss tangents,lowpermittivitytolerance,goodthermalconductivity,multilayeredsubstrate,cavities/embeddedcavities,lowmaterialcostsforsilverorgoldconductorpaths,easyintegrationwith othercircuits,andlowproductioncostsformediumandlargequantities.

Inourexperience,thePCBprocessispreferredforSIAdesignswhenanoperatingfrequencyis lowerthan60GHz,whileLTCCisagoodcandidateantennasoperatingatfrequencieshigherthan 60GHzandupto300GHz.Atfrequencieshigherthan300GHz,theLTCCfabricationbecomes quitechallengingbecauseofitsprocesslimitsuchasvia-holepitch.

1.6.2CommonlyUsedTransmissionLineSystemsforAntennas

Likeanyantennasystems,theirfeedingstructureswillbeacriticalissueintheimplementation oftheantennadesign.Inparticular,thelossescausedinthefeedingnetworksgreatlydegradethe

Figure1.5 SimplifieddescriptionsofPCBandLTCCprocesses.(a)PCBand(b)LTCC.

performanceoftheantennaarraysatmmWbands.Unliketheantennasatmicrowavebands,the lossescanbecausedbynotonlythedielectricsubstratebutalsometalsusedasconductorsfor transmissionandradiation.Likeanydielectricatmicrowavebands,thelossofadielectricsubstrate ismeasuredbyitslosstangent.Differentfromthedesignsatmicrowavebands,themetallossthat maybecausedbytheconductivityandsurfaceroughnessoftheconductorscan’tbeignored.

Besidesmicrostriptransmissionlines,thewaveguide-typetransmissionlinesystemsarepopularlyusedbecausetheymayenjoythelowerlossescausedbydielectricandmetalsatmmWbands [23–27,31].Accordingly,forinstance,thelossanalyseshavebeenconductedformicrostriplines, solid-metal-wallwaveguides,andpost-wallorlaminatedwaveguideorSIW[32].Thestudyshows thatingeneralthesolid-metal-wallwaveguideswithoutdielectriclossenjoylessmetallosswhile microstriplinessufferfromseveraldielectriclosses.Thepost-wallwaveguidesorSIWsfeature acceptabletotallossescausedbybothdielectricandmetallossesatmmWbands.However,itshould benotedthatthecausesoflossesoftransmissionlinesystemscanbecomplicatedbecausetheywill bedeterminedbythematerialssuchasdielectricandmetalsaswellasthetypesorconfigurations oftransmissionlines.

Thetransmissionlinesystemscanbeintheformofmicrostriplinesandcoaxiallines.Compared withconventionalcylindricalversions,thesubstrateintegratedcoaxialline(SICL)isatypeofplanarrectangularcoaxiallines.Thelinescompriseastripsandwichedbetweentwogroundeddielectriclayersandlaterallyshieldedbythearraysofmetallizedvias[33].Similartotheconventional coaxialline,thepropagationofSICLisstillinthedominantmodeoftransverseelectromagnetic (TEM).

TheSICLscanberealizedusingatraditionalmultilayerPCBorLTCCprocess.Therefore,SICLs featurethecombinedadvantagesofthecoaxiallinesandtheplanartransmissionlines,including thewidebandunimodaloperation,lowcost,non-dispersiveperformance,goodelectromagnetic compatibility,andeasyintegrationwithotherplanarcircuits.Ithasbeenusedforhigh-speeddata transmission[34]andvariousotherapplicationssuchasantennas,couplers,baluns,andfiltersat mmWbands[35–41].

Moreover,thesubstrateintegratedgapwaveguide(SIGW)orprintedridgegapwaveguide (PRGW)isproposedforthetransmissionlinesystemsatmmWbands.TheSIGWorPRGWis thecombinationofthemicrostrip-lineandgap-waveguidetechnologybasedonthePCBorLTCC

process[42–44].Theinvertedprintedstriplineisarrangedonorabovetheperiodicmushroom structureswheretheunwantedsurfacewavesaresuppressedandonlythequasi-TEMmodeis permittedovertheoperatingband.UnlikeSIWorSICL,thetopandbottomgroundsofaSIGW areunconnected.Therefore,theprocessingcomplexityisgreatlyreduced.TheSIGW/PRGW technologyhasbeenwidelyusedintheantennasandarraysatmmWbands[44–51].

Itshouldbenotedthattheselectionofthematerialsandtransmissionlinesystemssignificantly affectstheantennaefficiency.Thelossanalysesofantennasincludingtheirfeedingstructuresare stronglysuggestedtounderstandthemaincausesofthelossesinordertocontroltheoverallloss byproperlyselectingthematerialsandthetypesoftransmissionsystems,aswellasoptimizingthe designconfigurations[52].

1.7NoteonLossesinMicrostrip-LinesandSubstrateIntegrated Waveguides

Aspreviouslymentioned,tocompensateforthepath-lossathigherfrequencies,usuallyvery large-scaleantennaarraysarerequiredinmmWsystems.Insuchlarge-scaleantennaarrays thefeedingnetworkinevitablybecomescomplicatedwithalabyrinthoffeedingnetwork.The longcurrentorpowerpathsinthenetworkarethecriticalcausesfortransmissionlosses.The additionalunignorabletransmissionlossesmaybethestoppertolimittheachievementofhigh gainoflarger-scaleantennaarrayswhentheinsertionlosscancelstheincreaseinthegainby increasingthenumberoftheelementsofarrays.Forexample,iftheinsertionlosscausedbythe increaseofthepowerpathofthefeedingnetworkreachesnearly3dB,theantennaarraywith doublednumberofelementswillachieveverylittlegainenhancement.Therefore,itisimportant tocheckthetransmissionlinesystemsintermsofinsertionlossbeforethedesignofthearraysat mmWbands.

Next,theinsertionlossesinmicrostrip-lines(MSLs)andSIWsinLTCCat60GHzarecompared asanexample.TheLTCCisFerroA6-Mwithrelativedielectricconstant ��r = 5.9 ± 0.20,losstangent tanδ= 0.002at100GHz.TheconductorusedformetallizationandviasisAu,whoseconductivity is4.56 × 107 S⋅m 1 .

Figure1.6showsa10-mmlongbentMStransmissionlineonanLTCCboard.The50-Ω MSL iswithtwoportsinthesimulation.Figure1.7comparestheinsertionlossesforvaryingthicknessoftheLTCCboardoverafrequencyrangeof0–70GHz.Itisseenthatwhenthethickness increases,theinsertionathigherfrequencyedgequicklyincreases.Forinstance,thelosspercentimeterreachesupto13dBwhenthethicknessislargerthan0.7mm.

Figure1.8clearlyshowsthecausesoftheinsertionlossesathigherfrequenciesormmWbands. Thelossescausedbythedielectricsubstrateandconductorinthesystemarejustasmallpercentage ofthetotallosses.Itisbelievedthatat60GHz,thehigher-ordermodesexcitedbythediscontinuity oftheMScauselargesurfacewave(SW)/leakylossesaspreviouslydiscussed.Thisissueiseven severerforthethickersubstrate.SotheSWofMSatmmWisdefinitelyabigproblemforpractical antennadesign.

Figure1.9showsa10-mmlongbentSIWinanLTCCboard.Figure1.10showsthemainlossesat 60GHzofabentSIWinanLTCCboardwithvaryingthickness.Itisclearthatonthecontrary,the SIWsystemdoesnotsufferfromsuchadilemma,withthehighestlosslessthan1dBpercentimeter atsmallerthicknessesandtotallosseslowerthan0.6dBforathicknesslargerthan0.3mm.The low-lossfeatureisquitestableforallthethicknesses.Butactuallyfortheverythinthicknessof 0.1mm,theconductorlossishighfortheSIW.Fortunately,thethicknessof0.5mmisusually selectedforSIWat60GHz.Inparticular,themajorityoflossesarecausedbyboththedielectric andconductors,whichisdifferentfromtheMSlines.

1.7NoteonLossesinMicrostrip-LinesandSubstrateIntegratedWaveguides

of S-Parameters (dB)

Figure1.6 AbentMStransmission-lineonaLTCCboard. S21 S11

Thickness:0.1mm

Thickness:0.3mm

Amplitude of S-Parameters (dB) S21 S11

Thickness:0.5mmThickness:0.7mm

102030 Frequency(GHz) 040506070 S21S21 S11S11

102030 Frequency(GHz) 040506070102030 Frequency(GHz) 040506070 010203040506070

Figure1.7 Thecomparisonof|S11 |and|S21 |ofabentMStransmission-lineonaLTCCboard.

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